Tintinnoinea
Reproduction

Reproduction in tintinnids is commonly by binary division (tintinnid reproduction 1). However, sexual mechanisms (sexual reproduction 1, sexual reproduction 2, sexual reproduction 3) such as isogamic conjugation or fusion of micro- and macrogametes have also been described for a few species (Gold and Pollingher, 1971; Laval-Peuto, 1983). According to their proportions in the population during sexual reproduction, there is a random association of organisms with different lorical shapes (and even of naked individuals = trophonts; Laval-Peuto, 1983). Field studies have shown that in coastal and estuarine environments tintinnid reproduction rates are 1-2 generations per day (Heinbokel, 1978a; Burkill, 1982, Stoecker et al., 1983; Verity, 1986b), exceptionally up to 3 (Verity, 1987). On the other hand, generation times in oceanic waters are usually longer, up to 42 hours (Heinbokel and Coats, 1986; Heinbokel, 1987, 1988).

Cyst formation has been described for over 30 tintinnid species (Reid and John, 1978, 1983; Davis, 1985; Krisinic, 1987; Helicostomella subulata intro, Favella serrata intro, A. norvegica intro, cysts 1, cysts 2, cysts 3). Cysts are generally flask-shaped, and since they typically remain attached to the inner wall of the lorica, their specific identification is easier than for other protists. According to Reid and John (1981), highest concentrations of cysts are found in sediments, their record in the water column being only occasional. Recent information from sediment trap samples (Boltovskoy et al., 1993a; 1996; Uliana, 1997), however, suggests that flux rates of ciliate cysts in the water column at depths up to 4000 m can exceed 77,000 ind. mö-2 dö-1 (see geographic locations). Encystment, which is seemingly a common phenomenon in the life cycle of tintinnids, probably has a dual function: to provide a mechanism for repopulation as a response to environmental stress, and to revitalize the population after a bloom period, through the nuclear reorganization of the cell (Paranjape, 1980).